Prepare your vanilla or lemon cupcake batter. Fill your cupcake pan only about two-thirds full. (You may have to adjust your baking time for smaller cupcakes.) Once they're done, remove them from the pan and let them cool until they can be handled comfortably. If you weren't baking at 350 degrees Fahrenheit (176 degrees Celsius), readjust your oven to that temperature. Use a sharp knife to cut about 3/4 of an inch into each cupcake, and remove a small cone from the top. Spoon about a tablespoon of lemon curd filling into each of the holes, and plug the opening with the cone.

To make the meringue, beat the egg whites and cream of tartar in a large bowl with a whisk or a mixer on a low setting. Once it starts foaming and the cream of tartar dissolves, switch to medium speed and beat until peaks form. Continue beating while gradually adding the sugar.

Once finished, use a spatula to frost each cupcake with about 1/3 cup meringue. Place the cupcakes on a baking sheet, return them to the oven and bake until the meringue turns golden brown -- about 15 minutes. Cover, let cool for an hour, and refrigerate. Serve these cupcakes chilled.